Coastal Systems and Landscapes Flashcards
explain the different types of erosional processes
- hydraulic action is a when the power of waves hits the cliff face directly and forces water and air into cracks in the bedrock causing material to become dislodged
- solution/corrosion is when weak acids in seawater dissolve alkaline rock such as limestone
- attrition is when wave action cause rocks and pebbles to hit against each other, wearing each other down so that they become more rounded and smaller
- abrasion is a sandpapering effect in which sediment is dragged up and down the coastline, eroding and smoothing rocky surfaces
- wave quarrying is when breaking waves hit the coastline exerting pressure which scoops out loose unconsolidated material
explain the different types of transportation
-traction refers to the rolling of pebbles and larger sediment along the seabed
-saltation is the process where larger rocks are bounced along the sea bed
-suspension is the transport of small particles in the water, such as silts and clays, which produces a clouding effect
explain the different types of weathering
- freeze thaw weathering is when water enters the cracks and freezes causing the water to expand by 9 percent in volume which exerts pressure on the rock causing cracks to develop which makes its vulnerable to weathering
- crystallisation is when sea water enters cracks in the rock. when the sea water evaporates salt crystals are left behind. these crystals grow overtime exerting pressure on the rock which forces cracks to widen
- carbonation is when carbon dioxide in the air dissolves in rainwater to form a weak carbonic acid which reacts with calcium carbonate rocks to create calcium bicarbonate that can easily be dissolved
- oxidation is when rock becomes exposed to air through cracks and fissures their iron will be oxidised into a ferric state, which is known as rusting
describe longshore drift
- waves hit the coastline at an angle determined by the direction of the prevailing wind
- the waves push sediment up the beach at this angle as the swash
- due to gravity, the waves carry this sediment back down the beach at backwash perpendicular to the coast
- over a period of time, sediment is transported in a zigzag fashion along the coast
outline the process of wave formation
-wind moves across the surface of water contributing to fictional drag which creates small ripples. this leads to a circular orbital motion of water particles in the ocean.
-as the seabed becomes shallower towards the coastline, the orbit of water particles becomes more elliptical leading to more horizontal movement of waves.
what are sediment cells?
- sediment cells are sections of coastlines where the movement of sediment is contained within a closed system which are often bordered by two headlands
- the inputs within the sediment cell come from erosion of the sea bed or land such as cliff erosion
- there is little or no movement of sediment between the cells
- human activity can disrupt the natural system’s equilibrium
describe the formation of headlands and bays.
- along a discordant coastline there are alternating layers of soft and hard rock which are perpendicular to the coastline
- erosional processes attack the areas of softer, less resistant rock whilst the harder, more resistant rocks aren’t as vulnerable to erosion thus remain protruding from the coastline
outline the formation of swash and drift aligned beaches (depositional landforms)
-swash aligned beaches form when small sediments are deposited when waves break parallel to the coast. they typically form in low energy environment such as bays
-drift aligned beaches form when waves approach the coast at an angle determines by the prevailing wind and longshore drift transports material down the coastline
outline the development of barrier beaches (depositional landform)
- a barrier beach is usually formed as an extension of a spit
- longshore drift transports sediment along a coastline until there is a change in the shape of the coastline or a sudden interruption by a river estuary which causes the deposition of material to continue offshore.
- as the spit extends across a whole bay, a barrier beach forms which can be colonised by vegetation which stabilises the sand and traps further sediment
describe the formation of a spit (depositional landform)
- longshore drift is when waves hits the coastline at angle determined by the direction of the prevailing wind. the waves transport sediment up the beach as the swash and due to gravity the sediment is carried back down the beach as the backwash perpendicular to the coast. this transports sediment in a zigzag fashion along the coast
- when the mainland experiences a change in the shape of the land or the interruption of a river estuary it causes the deposition of sediment to continue offshore.
- if there is a change in the direction of the prevailing wind the spit can form a hook. due to the hook creating a sheltered area then a salt marsh should be created as salt-tolerant vegetation colonises
describe the formation of caves, arches, stacks and stumps (erosional landform)
-along a discordant coastline there are bands of hard and soft rock which are perpendicular to the coastline. this allows for the formation of erosional land forms like headlands and bays
- faults in the headland are exposed to erosional process such as hydraulic action and abrasion leading to the crack widening and a small cave forming
- occasionally, wave action and weathering causes joints in the cave rood to erode forming a blow hole
- the cave will expand due to marine and sub aerial erosion causing it to erode through the other side of the headland to create an arch
- the arch widens until it is unable to support itself so the roof of the arch becomes unstable and collapses forming a stack which is detached from the mainland
-sub-aerial and marine erosion can attack the stack causing it to form a stump
describe the formation of a wave-cut platform (erosional landform)
- when waves erode a cliff, the erosion is concentrated between high tide line and the low tide line
-the cliff begins to undercut, leading to the formation of wave-cut notch - as the wave-cut notch deepens due to marine erosion like hydraulic action and sub aerial weathering, the cliff face becomes unstable and collapses into the seabed below.
the contribute to the retreat of the cliff face and a build of sediment below
describe the process of sand dune succession
-dry sand grains are blown inland transported by saltation and rolling over the surface of the beach
-sand accumulates against a feature and builds upper beach height
-wind speed drops behind the accumulation contributing to further sediment deposition
-marram grass colonises the embryo dunes stabilising further dune migration and reducing the wind speeds so more sand is deposited.
-the decay of vegetation adds hummus to develop a soil horizon with more nutrients and moisture. this allows the colonisation of additional species
-as new sand dunes evolve towards heath and pine woodland inland the ecological succession is called the psammosere.
describe the process of mass movement
- rockfalls occur on mostly vertical cliff faces. rockfalls involve the sudden collapse or break away of rock fragments at a cliff face. it leads to the formation of a scree which is a build up of rock fragments on the base of a slope
- landslides occur when heavy rainfall causes water to enter into joint and bedding plains in the cliff face. this means the slip surface becomes lubricated so fraction is reduced. they tend to be very rapid.
-soil creep is the slowest but most continuous form of mass movement involving the movement of soil particles downhill due to wetting and freezing
-rotational slumping occurs on a sloped cliff face, typically when permeable rock overlies impermeable rock. the heavy rainfall is absorbed by unconsolidated material making up the cliff. a build up in pore water pressure causes the land to collapse under its own weight, leading to the formation of a scar.
benefits and drawbacks of groynes
-Groynes are long timber or concrete protrusions that are situated perpendicular to the coast. the groynes trap sediment which is transported by longshore drift to build up the beach height and width on the up drift side of the groyne, establishing a larger, wider beach. The creation of larger beaches will provide a more effective buffer against erosional processes as it absorbs the waves energy.
- groynes involve less investment from local councils as they only cost £400 per meter
- they create larger beaches which is a tourism amenity due to more space for tourist activities.
-promotes a positive feedback effect as longshore drift being halted deprives areas downwind of the groynes of sediment which increases the vulnerability to erosion there
benefits and drawbacks of a sea wall
- sea walls are concrete structures with re curved faces that reflect the wave energy back out to sea to dampen down the impact of erosional processes on the cliff face
- unaesthetically pleasing as it creates an artificial appearance to the coast
- they are expensive to construct as they cost £5000 per metre
- they can be used as a promenade which attracts tourism
- they are durable with a lifespan of 75 years
benefits and drawbacks of rock armour/rip rap
large rocks and boulders are placed at the base of a cliff in order to deflect wave energy and reduce the erosional impact on the cliff
-they typically use granite which is barely eroded even under high energy coastal environments, which often means they require less maintenance than a sea wall
- plants can establish in the rocks which increases the local biodiversity
- they are relatively cheap as they only cost £1000 to £3000 however it can be costly to extract and transport the the rocks
- the rocks are sourced from elsewhere which disrupts the natural local geology
describe ways in which sand dune ecosystems may be protected and managed
-sand dune ecosystems are significantly vulnerable to coastal processes and are challenging to sustainably manage.
-dune stabilisation involves planting perennial grasses and vegetation so the root can stabilise the sand into place
-dune fencing involves constructing fences along the seaward face of existing dunes which serves to keep animals and people away from the dunes to protect the environment. it reduces wind speed on the surface encouraging foredune deposition of transported sediment.
-dune thatching involves covering the dune face with plant debris and branches to stabilise the sand which acts as a low wind barrier to protect foredunes.
benefits and drawbacks of beach nourishments
beach nourishment is a process which involves replacing lost beach material from either offshore or from down shore
-it maintains natural shoreline without artificial intrusions
-low cost intervention for short time however regular costs will accumulate as the process must be perfromed repetitively over the year.
what are the shoreline management approaches?
-hold the line refers to intervention against erosion via hard and soft engineering strategies
-managed retreat is the realignment of the coast to a pre-determined line in order to redirect flooding from valued coastal areas to areas with less significance.
-advance the line is the extension of the coast into the seas
-no active intervention is a method that permits the natural systems to modify the coastline as they are continually operating.
describe the location of the holderness coast
The Holderness coast is located in East Yorkshire, in the North East of England. It extends 61 km from Flamborough in the North to Spurn Head in the South. Coastal erosion is occurring at an annual rate of 2 metres per year classifying the Holderness Coastline as one of Europe’s fastest eroding coastlines and contributing to the loss of at least 29 villages.
how does the lithology affect the development of the Holderness Coast?
the lithology of the coastline determines the rate of erosional processes. if a coastline predominantly consists of soft uncedemented rock types, the rock is more susceptible to marine erosion and sub aerial weathering as it is less resistant and has lower structural strength. On the other hand, coastlines predominantly consisting of resistant rock will impede fast rates of erosion.
The lithology of the holderness coast is comprised of a cretaceous chalk bedrock which is covered in a glacial till of soft boulder clay. The underlying boulder clay of the cliffs is susceptible to erosional processes as it is less resistant to the consistent force of the wave energy. For example, the exposed chalk at Flamborough head evidences examples of high erosion rates with the formation of erosional features including caves, arches and stacks.
how does the high energy coastline affect the development of the Holderness Coastline?
-The rates of marine erosion are influenced by the magnitude and type of waves reaching the coastline
-the Holderness Coastline is exposed to North-Easterly winds with a fetch of 500-800 km across the North Sea. Typically, this would not be a significant contributor to generating large waves however alongside this the coastline experiences currents from the Atlantic moving into the North Sea. With the Atlantic’s fetch of 5000km the current generates greater wave energy and the formation of destructive waves.
- Winter storms generated by the weather systems are intense in the North Sea, producing more powerful waves and sea level surges. the Rain carried over by the storms intensifies sub-aerial processes. the rainwater enters the boulder clay cliffs causing the material to undergo rotational slumping
what coastal management strategies have been implimented along the holderness coastline
- at Mappleton the coastline had experienced damages of £2.9 million previous to human intervention. currently, there have been rock groynes erected which halt the process of littoral drift in order to maintain wide beaches. Despite this, the groynes have starved the coastline down drift of material meaning coastal regions south of Mappleton have experienced significant increase in rates of erosion.
-at Withernsea a hold the line approach has been employed involving the construction of groynes and a sea wall. At £6.3 million the scheme has proven cost-effective with the aim of halting the declining property prices and saving the seasonal jobs in the resort.
